Chuck for lathe, grinding or milling machine

ABSTRACT

This invention relates to a mechanical chuck for a lathe, grinding machine, or milling machine which will automatically adjust the gripping jaws to provide equal support for the workpiece. The chuck is of the driving center variety, wherein the workpiece is centered and end-gripped. The chuck is designed to eliminate the disadvantages concomitant with hydraulic chucks, which tend to leak, jam, and need periodic servicing. A selflubricating feature is also provided.

United States Patent Anderson 51 Feb. 29, 1972 [54] CHUCK FOR LATHE,GRINDING OR 3,266,349 8/1966 Lane ..s2/40 MILLING MACHINE FOREIGNPATENTS OR APPLICATIONS m] Andemn 653,745 12/1937 Germany ..s2/40- [73]Assignee: Remington Arms Company, Inc., Reming- 177,173 8/1961 Sweden..82/40 ton Anns Company, Inc., Bridgeport, Conn. PrimaryExaminerLeonidas Vlachos Filed: Feb. 1970 Attorney-John H. Lewis, Jr.and Nicholas Skovran [21] Appl. No.: 13,535 [57] ABSTRACT This inventionrelates to a mechanical chuck for a lathe, grind- 52 us. 01. ..s2/4o,51/237 R s machine, of milling machine which will automatically [51] kmn B23, 33/00 just the gripping jaws to provide equal support for thework 58 Field of Search ..82/40' 51/236, 237 R Plece- The chuck isdriving camel valielywherein workpiece is centered and end-gripped. Thechuck is designed to eliminate the disadvantages concomitant withhydraulic [56] References Cited chucks, which tend to leak, jam, andneed periodic servicing.

UNITED STATES PATENTS A self-lubricating feature is also provided2,909,955 10/1959 Williams ..82/40 7 Claims, 7 Drawing Figures I'm ehfor" SHEET 2 OF 3 0000/5 J Anderson d. H m [2 M PAIENTEBFEBZS m2fitter/revs fjrwmz PATENTEUFEB29 m2 SHEET 3 [IF 3 [/7 ventar Dennis 41findersan CHUCK FOR LATHE, GRINDING R MILLING MACHINE The inventionpertains to a chuck for a lathe, grinding machine, or milling machineand more particularly to an adjustable chuck of the driving centervariety for end-gripping a workpiece.

The driving center chuck provides many advantages over the prior methodsof constraining machining materials. For example, a shaft which isend-gripped by a driving centered chuck, can be completely machined fromone end to the other. This eliminates additional machining operations.

Correction was previously required for those end areas which wereformerly inaccessible to the machining tool or which had to beremachined for having been marred by the clamping teeth of the chuck.

Material savings and reduced setup time are also realized by the newmethod.

With the many advantages expressed by end-gripping, there are also manyproblems. Precise force alignment has to be maintained amongst 1 theseveral gripping jaws, since the slightest maladjustment can cause theworkpiece to slip while spinning. This is often caused by anout-of-square condition on the gripped end of the workpiece. Thisslippage cannot be tolerated because the workpiece can then fly out ofthe lathe, causing damage and injury. Also, unequal forces on thegripping jaws causes bending in slender shafts (gun barrels), makingmachining very difficult.

As a result'of the aforementioned requirement, the jaws of the chuck aremade to equalize the end forces between them. The common method ofaccomplishing this equalization is to have the individual jaws transmittheir end forces to a fluid medium. This medium distributes the forcesback to the jaws, so that each gripping member can be in equal contactwith the workpiece (Pascals theory).

The obvious disadvantage of employing hydraulics, however, is that thefluid medium has a tendency to leak or become contaminated. Thus, it isvery common for these chucks to jam, or otherwise become inoperative.

The present invention is for a chuck which will accomplish the variousobjectives set forth for driving center devices, but which willeliminate the problems concomitant thereto.

The present system is predicated upon an exclusively mechanical means ofequalizing the jaws. As such, the problems of leakage and contaminationof the liquid medium are nonexistent.

Several other attempts have been made to provide a mechanicalequalization or adjustment feature in chucks. Reference is hereby madeto patents issued to Sloan, U.S. Pat. Nos. 2,698,185, issued Dec. 28,1954; and 2,524,485, issued Oct. 3, 1950.

The present chuck has many distinct differences and advantages over theSloan chucks.

In the first instance, the Sloan devices do not represent endgrippingchucks as does the subject invention.

In the second place, the invention tries to distribute the forces over awide surface area (spherical cap) so that adjustment and alignmentapproaches its truest potential. The small spherical ball of the Sloandevices tends to create precise alignment, and tolerance problems. Byspreading the forces over a larger sliding surface, the present chuckeliminates costly precision parts. In addition, any inconsistencies inthe surface of the spherical cap and its mating depression will wearthemselves into a truer alignment with use, while this does not appearto be the case with the ball of Sloan.

The U.S. Pat. No. 2,698,185 has many more moving parts than the presentsystem, which obviously makes for a more costly and complicatedstructure. The U.S. Pat. No. 2,524,485 patent shows a high-friction-typeconnecting link between the jaws and the universal ball centering means.The present chuck is simple in operation compared to the Sloan devices,and attempts to reduce friction to the minimum so that equalization ofthe jaws will be smooth and trouble-free. The reduction of friction ishighly essential in order to produce true equalization of the endforces. To this end, this invention 2 III! contemplates usingfrictionless materials on all sliding, mating or moving surfaces and/orlubricating or coating said surfaces with frictionless materials.

It is to be noted, however, that the increase in mating surface area inthe present device does not necessarily increase the frictional forces.The frictional force F on the sliding surfaces is generally given by theformula:

m I- N where:

N is the normal force exerted on the mating surface; and

p. is the coefficient of sliding friction between the mating surfaces.

Thus, it is evident from the above formula, that surface area is not aparameter that influences the frictional effects of the mating parts.

Reference is also made to the patent issued to Carmi et al., U.S. Pat.No. 3,158,39l, issued Nov. 24, 1964. This patent discloses annularspherical mating parts not unlike the present system. It is to be noted,however, that Carmi et al. neither teaches nor shows how this device maybe employed for application in the chuck art, nor does he explain how toalign three separate contact members (jaws).

It is an object of the present invention to provide a driving centerchuck for end-gripping a workpiece, which will equalize the end forcesupon the gripping jaws by mechanical means.

It is another object of this invention to provide a driving center chuckwhich will be devoid of the problems usually associated with chucksusing hydraulic means to equalize the jaws.

It is a contemplation of this invention to provide a mechanical chuckwhich will freely equalize the forces amongst the gripping jaws byemploying frictionless materials in strategic areas of mechanicalalignment and connection.

It is still another object of this invention to provide a chuck which isself-lubricating.

It is a further object of this invention to provide a chuck of thedriving center variety which is reliable in operation, requires littleif any maintenance, and is inexpensive to manufacture.

These and other objects of the invention will present themselves andbecome more evident from an understanding of the subsequent detaileddescription and the accompanying drawings in which:

FIG. I shows a front view of the chuck of this invention;

FIG. 2 depicts a side view of the chuck, but through section lines A-Aof FIG. 1;

FIG. 3 illustrates a sectional side view of the chuck embodying anautomatic lubricating reservoir;

FIG. 3a is a blowup view of a particular feature of FIG. 3;

FIG. 4 shows the chuck of FIG. 3 containing lubricant while at rest;

FIG. 5 depicts the chuck of FIG. 3 containing lubricant while rotating;and

FIG. 6 illustrates an alternate embodiment for the jaws of the chuck.

Generally speaking, the invention is for an adjustable chuck of thedriving center variety for end-gripping a workpiece. There are severalnovel features in the chuck, one being an adjustment means and anothercomprising a self-lubricating system.

The chuck comprises a housing having its axis of rotation extending froma front face portion to a rear portion thereof. A baseplate is rigidlysecured within the housing. The surface of the baseplate has an annularspherical depression. A movable member makes slidable mating contactwith the baseplate by means of an annular spherical protuberance whichhas a radius of protrusion like that of the radius of depression in thebaseplate, so that both protuberance and depression are in substantialsurface conformity with each other. A plurality of jaws for the purposeof gripping the workpiece are disposed upon the front face portion ofthe housing angularly spaced thereabout in substantially equal array.The jaws are individually connected to the movable member and are freeto coaxially move with respect to the rotational axis of the housmg.

When a coaxial force is applied by the workpiece to any one or more ofthe jaws, the jaws will transmit the force to the movable member causingit to slide upon the baseplate and thereby adjust the jaws to a positionof substantially equal support for the workpiece. v

The transmission of-the workpiece end forces is further accomplished bya plurality of tiltable toggle links each of which contains aball-socket and linking ball assembly. The ballsocket portion of eachassembly is connected to the slidable member, and the linking balls areindividually connected to one of the gripping jaws. When a force isexerted on any one or more of the jaws, it is communicated through therespective ball and ball-socket assemblies to the slidable member,causing it to move in adjustive response to the force.

The mating surfaces of the protuberance and depression should be made asfrictionless as possible to facilitate the adjustment of these partsunder light loads. Also, the toggle assemblies should be as frictionlessas possible for similar reasons. The reduction of the friction can beaccomplished in several ways such as:

a. making all moving or mating surfaces of frictionless materials ormaterials which can be impregnated with friction relieving substancessuch as graphites or oils, etc.

b. coating the moving metallic parts with coatings of frictionlesssubstances such as teflon or other solid or dry film lubricants, and

c. keeping all parts well lubricated by means of internal oilreservoirs, wherein the oil is fed to the necessary parts undercentrifugal force and/or by capillary action.

In conformity with the aforementioned objectives, an automatic orself-lubricating feature is provided for the chuck.

Self-lubrication is considered by the inventor to be an innovation inthe mechanical chuck art. Although the present invention shows aparticular means of automatically lubricating the mechanical operatingparts of the chuck, other methods or means may be fashioned to achievethis purpose that are not inconsistent with the spirit and scope ofthisinvention.

Generally speaking, the automatic lubricating means comprises areservoir of lubricant internally disposed within the chuck housing.

The reservoir has a metering aperture to periodically supply a givenamount of the lubricant to the mechanical parts of the chuck.Distribution of the lubricant is achieved by centrifugal force, when thechuck is put under rotation. Distribution to remote parts of themechanical system is also achieved by providing small holescommunicating with the reservoir which feed the lubricant from thereservoir to the desired parts by capillary action.

Either centrifugal force or capillary action can be used or acombination of the two for the above purposes.

Now referring to FIG. 1, a front view of the chuck of this invention isshown. The face of the chuck is given as 1. Three gripping jaws aredisposed upon the face of the housing in equal array about the axis ofrotation R (see FIG. 2). A typical gripping jaw is represented as 2, andeach jaw has a biting tooth 17 for end-gripping the workpiece. The jawsrest within the jaw holders 5, and can be adjusted for differentworkpiece sizes by moving the jaws toward or away from the axes ofrotation as shown by arrows 26. When the proper setting is achieved, thejaws are locked into place within the jaw holders (not shown).

Now referring to FIG. 2, a sectional side view of the chuck is shown astaken along lines A-A of FIG. 1.

The housing of the chuck is given as 8. A baseplate 7 is affixed to thehousing at the rear thereof. The baseplate has an annular sphericaldepression with its concave surface facing the front of the chuck.Resting within the depression is a cap 3 (an annular sphericalprotuberance) having a radius of convexity similar to the radius ofconcavity of the depression so lllld that both parts conform orotherwise mate with each other as depicted by surface 12.

The cap 3 has a flat surface 14. Three toggle assemblies 6 are incontact with surface 14. The toggle assemblies each have a ball-socket 9in which a toggle ball 19 rests. Each assembly is individually connectedto a gripping jaw 2 by means ofa link 21 which is pinned at 15 to thejawholder 5.

In operation, the chuck center 4 contacts the workpiece (not shown).This action is independent of the gripping teeth, which is not alwaysthe case in other driving centers. The center 4 is biased intoengagement by a spring (not shown). The workpiece then contacts theteeth 17 of the gripping jaws 2. FIG. 2 shows two different forces, Fand F, respectively, exerted by the workpiece and acting upon the teeth.If these forces are not in balance, i.e., not equal in magnitude, thenthe system will adjust the positions of the gripping jaws so that theyeach equally support the workpiece. This is accomplished in thefollowing manner:

The jaws 2 are free to move coaxially with respect to the rotationalaxis R, so that any force or forces exerted by the workpiece upon theteeth 17 will cause the jaws 2, and consequently the jaw holders 5, tomove.

These forces are subsequently exerted upon links 21 which are pinned tothe jaw holders 5 at point 15. These forces are transmitted to toggleassemblies 6 which are free to tilt. This tilting action will exert aforce upon surface 14 of cap 3, causing the cap to slide upon baseplate7 as is generally depicted by arrows 16. The cap 3 will be displaced inthe direction of the least force, which is that direction in which agripping jaw is not bearing its share of the workpiece load.

In so shifting, the cap will exert a force back upon the linkage of thegripping jaw bearing the lesser force. This will cause the jaw to reseatitself with respect to the workpiece and will result in adjusting thejaws to a position of equal support of the end gripping forces.

Now referring to FIG. 3, an automatic lubricating reservoir is shown forthe chuck. The reservoir 29 is filled by means ofa hydraulic fitting 39which is recessed in countcrbore 30. The oil (lubricant) flows throughline 28 into reservoir 29 which forms part of baseplate 7. A smalltapered metering hole 35 communicates with the reservoir (see FIG. 3A).This metering hole will entrap a small given amount of oil which willflow along surface 12 under centrifugal force (when the chuck isrotating). The oil will also flow into capillary hole 36 when this holeis in proper alignment with the metering hole 35 as shown.

In practice, several of these small holes (36) may be provided to suckthe oil from hole 35, when the cap 3 is in different positions withrespect to the baseplate 7. Continuous flow from the metering hole 35 isblocked, however, when the chuck is at rest (not rotating), as isobservable with reference to FIG. 4. The height of the lubricant 41 isdepicted by When the chuck is in this position oil will flow into hole35, but will be blocked from flowing into hole 36. Neither will thelubricant flow along edge 12, because the chuck is not rotating. The oilis prevented from leaving the tapered metering hole, because the cap hasslumped to a position blocking hole 35 as is shown by arrow A. Slumpingtoo far out of alignment, however, is prevented by contact of shoulder25 of the jaw holder 5 with that of the flange B of the housing 8.

When the chuck is rotating as is illustrated in FIG. 5, oil will notcontinuously flow out of the hole 35, because the metering hole is notin contact with its reservoir supply. The lubricant in the reservoir isforced outward under centrifugal force as is shown by arrows C, leavingno lubricant in contact with hole 35.

Lubricant is trapped, however, in hole 35 from the previous instancewhen the chuck was at rest (see FIG. 4). This oil is now distributed tosurfaces 12 and 14 under the action of centrifugal force and capillaryaction.

Thus, it is seen that the aforementioned arrangement distributes a givenamount of oil during its operation, and is selflubricating in the truestsense of the word. It must be noted that the size of the holes 35 and 36will determine the quantity of the lubricant fed to the system. It mustalso be noted that the mating surfaces at 12 are also critical in theproper distribution of oil.

Of course, many modifications may be made in the above system--forexample, each toggle may have its own reservoir built into the assembly,with its individual metering hole. Several interconnecting reservoirscan be employed within the housing to furnish lubricant to various partsof the mechanical mechanism.

FIG. 6 depicts an alternate jaw arrangement for the chuck. The jawholder 5 is provided with a slot to accommodate the gripping jaw 52. Thegripping jaw has two teeth shown as 59 and 59', respectively. The jaw 52is anchored to the jaw holder 5 by means of a pin 50 which fits the hole54 of the jaw holder, and also fits through hole 51 of the gripping jaw.The pin 50 is keyed (not shown) to prevent rotation.

Obviously, many modifications and variations may be made in thisinvention which are apparent to those skilled in the art. Such changesare considered to be within the spirit and scope of the invention asdepicted by the appended claims.

What is claimed is:

1. An adjustable chuck of the driving center variety for endgripping aworkpiece comprising:

a housing having its axis of rotation extending from a front faceportion to a rear portion thereof;

a baseplate rigidly disposed within the housing and having an annularspherical concave depression in a surface of said plate; movable memberin slidable mating contact with the baseplate, said member having anannular spherical convex protuberance with a protrusive radius of likeconvexity as that of the radius of concavity of said baseplate, whereinsaid protuberance is in substantial surface conformity with thedepression;

a plurality of jaws for gripping a workpiece, said jaws disposed uponthe front face portion of the housing angularly spaced about the frontface portion in substantially equal array, said jaws individuallyconnected to the movable member and free to coaxially move with respectto the rotational axis of said housing, whereby any force, coaxial indirection to the rotational axis of the housing, which is exerted by theworkpiece upon any one or more of the jaws, will be transmitted by thejaws to the movable member causing it to slide upon said baseplate andthereby adjust the jaws to a position of substantially equal support forsaid workpiece; and a plurality of tiltabie toggle links each containinga ball-socket and linking ball assembly, respectively, the ball-socketportion of each assembly being connected to said slidable member, andeach linking ball being connected to an individual gripping jaw,respectively, whereby a coaxial force upon any one or more of the jawswill be communicated through the respective ball and ball-socketassemblies to the slidable member and cause said member to move inadjustive response to the force.

2. The adjustable chuck of claim 1, wherein the mating surfaces of thebaseplate depression and the protuberance of the movable member aresubstantially coated with a friction reducing substance whereby thebaseplate and movable member are rendered more favorably movable withrespect to each other.

3. The adjustable chuck of claim 1, wherein the baseplate and movablemember are composed of a substantially frictionless material, wherebythey are rendered more favorably movable with respect to each other.

4. The adjustable chuck of claim 1, wherein there are three jaws forgripping the workpiece.

5. The adjustable chuck of claim 4, wherein there are two teeth on eachgripping jaw, respectively.

6. The adjustable chuck of claim 1, wherein the mating surfaces of theball and ball-socket assemblies are substantially coated with a frictionreducing substance so as to render the to le more favorably tiltable.

. The adjustable chuck of claim 1, wherein the ball and ball-socketassemblies of said toggles are composed of a substantially frictionlessmaterial, hereby the toggle is rendered more favorably tiltable.

1. An adjustable chuck of the driving center variety for endgripping aworkpiece comprising: a housing having its axis of rotation extendingfrom a front face portion to a rear portion thereof; a baseplate rigidlydisposed within the housing and having an annular spherical concavedepression in a surface of said plate; a movable member in slidablemating contact with the baseplate, said member having an annularspherical convex protuberance with a protrusive radius of like convexityas that of the radius of concavity of said baseplate, wherein saidprotuberance is in substantial surface conformity with the depression; aplurality of jaws for gripping a workpiece, said jaws disposed upon thefront face portion of the housing angularly spaced about the front faceportion in substantially equal array, said jaws individually connectedto the movable member and free to coaxially move with respect to therotational axis of said housing, whereby any force, coaxial in directionto the rotational axis of the housing, which is exerted by the workpieceupon any one or more of the jaws, will be transmitted by the jaws to themovable member causing it to slide upon said baseplate and therebyadjust the jaws to a position of substantially equal support for saidworkpiece; and a plurality of tiltable toggle links each containing aball-socket and linking ball assembly, respectively, the ball-socketportion of each assembly being connected to said slidable member, andeach linking ball being connected to an indIvidual gripping jaw,respectively, whereby a coaxial force upon any one or more of the jawswill be communicated through the respective ball and ball-socketassemblies to the slidable member and cause said member to move inadjustive response to the force.
 2. The adjustable chuck of claim 1,wherein the mating surfaces of the baseplate depression and theprotuberance of the movable member are substantially coated with afriction reducing substance whereby the baseplate and movable member arerendered more favorably movable with respect to each other.
 3. Theadjustable chuck of claim 1, wherein the baseplate and movable memberare composed of a substantially frictionless material, whereby they arerendered more favorably movable with respect to each other.
 4. Theadjustable chuck of claim 1, wherein there are three jaws for grippingthe workpiece.
 5. The adjustable chuck of claim 4, wherein there are twoteeth on each gripping jaw, respectively.
 6. The adjustable chuck ofclaim 1, wherein the mating surfaces of the ball and ball-socketassemblies are substantially coated with a friction reducing substanceso as to render the toggle more favorably tiltable.
 7. The adjustablechuck of claim 1, wherein the ball and ball-socket assemblies of saidtoggles are composed of a substantially frictionless material, herebythe toggle is rendered more favorably tiltable.